1. Field of the Invention
The present disclosure generally relates to electrodes that are used in nerve stimulation. More particularly, the present disclosure relates to helical electrodes for nerve stimulation, such as vagus nerve stimulation.
2. Description of the Related Art
Since its introduction, nerve stimulation has been used to treat a variety of neurological conditions. Vagus Nerve Stimulation (VNS) is one type of nerve stimulation that has been used as a treatment for intractable epilepsy. Typically, this involves stimulating the left cervical vagus nerve via an implanted electrode (the vagus nerve can also be stimulated outside of the cervical area and on the right vagus). VNS has been available for clinical treatment of epilepsy in the U.S. since 1997. The therapy is achieved through an implanted pulse generator that delivers a bipolar, biphasic pulse. The implant procedure is very similar to the implantation of a pacemaker. The generator is implanted subcutaneously, typically in the upper left chest wall. An electric lead is connected between the pulse generator and the electrode using a subcutaneous tunneling tool to the vagus nerve, which lies in the carotid sheath.
Traditional nerve stimulation electrodes utilize a nerve cuff (a cylinder with an open side) that is placed around the nerve and sutured closed. In recent years, helical electrodes have been developed as an alternative to the nerve cuff because they provide a “self-sizing” feature by allowing the electrode to expand and contract to account for post-implant inflammation and ingrowth of fibrotic tissue between the nerve and electrode without increasing pressure on the nerve. Current VNS electrodes are frequently fabricated from a platinum-iridium alloy embedded in flexible silicon. The electrodes are helical in shape, and consist of an anode, a cathode and a tether helical (which serves to anchor the anode and cathode but does not itself contain an embedded metal electrode).
It is desirable for helical electrodes to provide effective nerve stimulation with minimum power consumption. It is believed that current electrodes fall short in this area. The present disclosure is directed to overcoming, or at least reducing the effects, of one or more of the issues set forth above.